The present invention relates to the field of photography and, more specifically, to photographic apparatus for exposing a plurality of image areas on a single card-like film unit.
Commonly-assigned copending applications U.S. Ser. Nos. 071,939; 071,940 (now U.S. Pat. No. 4,235,545); and 072,051 (now U.S. Pat. No. 4,235,543), all filed on Sept. 4, 1979, describe and claim various aspects of a microfiche system for sequentially recording micro images of a plurality of different documents on a single card-like film unit, preferably of the self-developing type, and, after film processing, for projecting enlarged images of the documents from the film into a viewing screen.
The system comprises a camera, projector and a console having a combination document mounting and viewing screen area and a mount for alternatively receiving the camera or projector.
In the recording mode the camera is located in the mount and documents to be copied are successively supported on a mounting glass. The camera includes a scanning lens system for incrementally advancing the lens laterally along a portion of the film to successive imaging positions for exposing a row of image areas thereon. After each row is exposed, the film unit is advanced longitudinally one row position in preparation for exposing the next row of image areas. After all the image areas are exposed, the film unit is advanced between a pair of pressure rollers for processing.
To convert the system to the viewing mode, the mounting glass is covered with a viewing screen and the camera is replaced by the projector which is operative to project an enlarged image of any document recorded on the film unit onto the viewing screen.
The present invention is directed to the structure and operation of an imaging system that may be used during the recording mode of operation of such a microfiche system and more particularly to means for automatically advancing the lens in increments to accurately center an image of a document, supported at the mounting glass, with respect to each of the image areas in the row.
Multiple image cameras are well known in the prior art. One type utilizes a fixed lens and mounts the film unit for movement relative thereto to present successive portions of the film unit at an exposure position in direct alignment with the lens. The advantage of such a system is that the lens remains aligned with the subject or a fixed object plane. The disadvantage, however, is that the back of the camera must be much larger than the size of the film to accomodate such film movement. For examples of such cameras see U.S. Pat. Nos. 2,660,920 and 3,667,364.
Another type of camera utilizes a fixed film plane and mounts the lens for movement relative thereto.
For examples, see U.S. Pat. Nos. 3,503,317; 4,027,315 and 4,140,381.
Generally, these cameras are used in photographic situations where the subject is relatively far away and/or does not fill the entire image area on the film so that the shift of the lens relative to the film plane is not noticeable.
However, when the subject is close, the shift in lens position causes a significant shift of the image with respect to the film plane and the image may not lie in the desired image area.
For example, U.S. Pat. No. 1,892,683 describes a graphic arts camera having a movable lens. The camera is used to photograph objects mounted on a copy stand at a relatively short distance therefrom. To compensate for the shift in image position due to lens movement, the object location is moved on the copy stand so that the object is always aligned with the lens.
In the microfiche system described earlier, the object to be photographed (a document) is mounted and centered at a fixed object plane which is relatively close to the camera lens. It is intended that an image of the document fill the entire image area for most efficient use of the film. When the lens is moved to a position that is offset with respect to the object plane center and is centered with respect to a corresponding image area the resultant image is shifted and does not lie entirely within the image area.
This problem is well known in the photographic art and is most prevalent in photographing large objects such as buildings. Because the camera is at ground level and not aligned with the center of the building, the entire building generally does not fall within the camera field of view unless the camera is tilted upwardly. This in turn sets the film plane in non-parallel relation to the object plane and will by necessity cause perspective distortion. However, this problem may be overcome by using a camera having a rising and/or cross front in which the film plane is set parallel to the object plane and the lens is shifted off axis with respect to the film plane to center the image thereon. This technique also may be used to make stereoscopic photographs of large objects wherein the lens is shifted relative to the film plane at off axis camera locations as suggested in U.S. Pat. No. 3,494,270.
On the one hand, providing a multiple image camera with a lens that moves relative to the film plane (at least in one direction to photograph a row or column) allows the camera to be made in a more compact manner than if the camera is configured to have its film plane shifted both horizontally and vertically. On the other hand, however, the movable lens may cause image shift problems in those applications where the object is close at hand and the image is intended to fill the entire image area unless suitable corrections are made.
Therefore, it is an object of the present invention to provide a photographic apparatus for exposing a plurality of image areas on a single card-like film unit wherein the lens is automatically moved in increments relative to the center of a fixed object plane to compensate for image shift such that the image of an object centered at the object plane is centered with respect to corresponding image areas at the film plane.
It is another object to provide such a photographic apparatus that is simple in construction and is suitable for use in a low cost microfiche system.
It is another object of the invention to provide a multiple image photographic apparatus having a lens that is movable relative to the film plane and means for automatically advancing the lens relative thereto in predetermined increments to center the image provided by the lens with respect to both aligned and offset image areas.
Other objects of the invention will, in part, be obvious and will, in part, appear hereinafter.